Cardio exacerbating anxiety?

Are you training for something? Are you pushing yourself, looking for results? That could be adding to your anxiety levels--I'm much more intense when training for something than when I'm just doing maintenance.

Have you discussed with your doc? Do you have any mitral valve issues?

Maybe a related issue......recently passed up a chance to compete in an international "vertical challenge" race as I could envision having a panic attack during it. Don't normally suffer from generalized anxiety but exposed heights (oddly, unless I'm climbing a mountain), injections, driving fast on open interstate (probably a form of motion sickness since I'm used to third world speeds) and small enclosed places tend to give me the heebie jeebies, and I tend to have a strong physical response in very stressful situations (sweating, intense nausea, etc.) I find physical symptoms of anxiety are worse if my heart's already pounding anyway from exertion.  I think the elevated heart rate from exercise tricks the brain into thinking an anxiety attack has already started, then it escalates--physical symptoms of anxiety, concern about the physical symptoms, more anxiety, etc. If you can find any kind of biofeedback device, even a heart rate monitor, and try to slow your heart rate through rhythmic breathing, meditation, etc. it can be useful in controlling physical symptoms of anxiety. I'd also rule out purely physical causes of your symptoms, and avoid caffeine!